A model for the oven rise of dough during baking

A model for dough expansion during oven rise, under conditions where the te mperature is independent of position, is presented. The growth of a single gas bubble as a result of the generation of carbon dioxide and water vapour from the surrounding viscous dough is considered. The resulting equations were solved using appropriate numerical methods. The predicted results for oven rise show that the dough volume increases almost linearly with time un til a temperature of about 65 degrees C is attained. Above this temperature , the dough expands at a reduced rate and the cell structure starts to set at 85-90 degrees C. The bubble pressure relative to atmospheric pressure is 1.008 in the early stages of expansion, but rises to 1.3-1.4 prior to sett ing of the dough. The model also indicates that during the initial baking s tage the bubble growth is entirely controlled by the partition of carbon di oxide and water vapour between the aqueous and bubble phases. Viscous resis tance to bubble growth is important in the later stages of oven rise when t he viscosity exceeds similar to 5.0 x 10(5) Pa s. The model shows that it i s possible for the eventual termination of oven rise to be caused by the ra pidly increasing viscosity which enhances the resistance to bubble growth. Even though elasticity is not taken into account, the predicted dough volum es are found to be in reasonably good agreement with published data for dou gh baked in a resistance oven, although the bubble pressure at the end of o ven rise is higher than predicted. It is suggested that in some cases the c ell rupture resulting in the open cell structure for bread could be a conse quence of the increased pressure and not the cause for the termination of o ven rise. (C) 1999 Elsevier Science Ltd. All rights reserved.